Fatigue Measurement
Research in this area is highly heterogeneous in the assessment of fatigue given its multidimensional nature (Onate-Figuérez et al. 2023). Measurement of fatigue could be performed via objective methods such as fatiguing tasks or subjective measures such as self-reporting methods to describe the perception of fatigue (Onate-Figuérez et al. 2023). These self-reports also serve to evaluate perceived fatigue intensity or its effect on the participants’ lives (Onate-Figuérez et al. 2023).
The studies included in this systematic review measure fatigue using self-reports, with the Fatigue Severity Scale (FSS), being the most common measure. The FSS is a 9-item self-report questionnaire that evaluates the severity of fatigue and its impact on lifestyle and activities (Curtis et al. 2015), covering three domains: physical, social, and cognitive effects of fatigue (Hewlett et al. 2011). It has high validity and reliability (Cronbach α = 0.89, intraclass correlation coefficient, 0.84; 95% confidence interval [CI], 0.74 – 0.90) for evaluating fatigue in people with SCI (Anton et al. 2008). More information about the FSS is available on the SCIRE Professional webpage: Fatigue Severity Scale.
Other less commonly used measures included the Chalder Fatigue Scale (CFS), the Multi-Dimensional Fatigue Inventory (MFI-20), the Modified Fatigue Impact Scale (MFIS), the PROMIS Short Form v1.0 Fatigue 8a, or the Fatigue Assessment Scale (FAS). The CFS is a self-rated fatigue scale that provides an overall indicator of chronic fatigue, as well as domains of mental and physical fatigue (Chalder et al. 1993). The MFI-20 was originally developed for cancer patients and covers five dimensions: General Fatigue, Physical Fatigue, Mental Fatigue, Reduced Motivation, and Reduced Activity (Hagelin et al. 2007; Smets et al. 1995). The MFIS is a 21-item shortened version of the 40-item Fatigue Impact scale that examines the perceived impact of fatigue in three areas: cognitive functioning, physical functioning and psychosocial functioning during the past four weeks (Fisk et al. 1994; Shem et al. 2016; Wong et al. 2023). The PROMIS Short Form v1.0 Fatigue 8a evaluates fatigue based on its frequency, duration, and intensity, as well as its impact on physical, mental, and social activities (Cella et al. 2010; Wong et al. 2023). The FAS is a 10-item scale evaluating symptoms of chronic fatigue which treats fatigue as a unidimensional construct and does not separate its measurement into different factors (Shahid et al. 2012). Further, there were other interventional studies which used the fatigue subscale of the Profile of Moods States (POMS), the vitality subscale of the SF-36, a numerical rating scale, or a visual analog scale for measuring fatigue in people with SCI.
In summary, although different outcome measures for fatigue have been used in SCI research, the FSS is the only (and most used) outcome measure that has been validated in people with SCI. In addition, the 7-item version of the FSS has been recently recommended as a primary outcome measure in stroke research (English et al. 2023). Thus, the use of the FSS should be recommended in future studies assessing fatigue in people with SCI.
